The Greeks became masters of the Mediterranean Sea out of necessity and due to their innovation.
The Greek mainland is very mountainous and rocky. The soil is not fertile enough to support large populations. Consequently, the Greeks looked to the seas for trade in order to secure goods that they could not produce themselves. After traveling for trade throughout the Mediterranean, colonies were established in every direction. Because Greece is a peninsula, the Greek city-states needed to defend their coastlines and it was a necessity to develop a strong navy.
The Greeks adopted many shipbuilding techniques and other technologies from the Phoenicians. They improved on these shipbuilding techniques and developed technologies like the astrolabe to navigate the Mediterranean Sea. They used their skill in astronomy to travel the seas in every direction. To improve future trips, ship’s captains routinely kept logs describing landmarks along coastlines.